Semiconductor device

ABSTRACT

A semiconductor device includes a fin-shaped silicon layer and a pillar-shaped silicon layer on the fin-shaped silicon layer, where a width of the pillar-shaped silicon layer is equal to a width of the fin-shaped silicon layer. Diffusion layers reside in upper portions of the pillar-shaped silicon layer and fin-shaped silicon layer and in a lower portion of the pillar-shaped silicon layer to form. A gate insulating film and a metal gate electrode are around the pillar-shaped silicon layer and a metal gate line extends in a direction perpendicular to the fin-shaped silicon layer and is connected to the metal gate electrode. A contact resides on the metal gate line and a nitride film is on an entire top surface of the metal gate electrode and the metal gate line, except for the bottom of the contact.

RELATED APPLICATIONS

This application is continuation application of U.S. patent applicationSer. No. 14/469,107, filed Aug. 26, 2014, which is a continuation ofU.S. patent application Ser. No. 14/177,459, filed Feb. 11, 2014, whichis a divisional patent application of U.S. patent application Ser. No.13/891,655, filed May 10, 2013, which claims benefit pursuant to 35U.S.C. §119(e) of U.S. Provisional Patent Application Ser. No.61/648,817, filed May 18, 2012. The entire contents of which are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device.

2. Description of the Related Art

Semiconductor integrated circuits, in particular, integrated circuitsthat use MOS transistors, are becoming more and more highly integrated.As the circuits achieve higher integration, the size of MOS transistorsused therein is reduced to a nanometer range. With smaller MOStransistors, it sometimes becomes difficult to suppress leak current andto decrease the area occupied by the circuit since a particular amountof current is required. Under these circumstances, a surrounding gatetransistor (hereinafter referred to as SGT), which includes a source, agate, and a drain arranged in perpendicular to a substrate, the gatesurrounding a pillar-shaped semiconductor layer, has been proposed (forexample, refer to Japanese Unexamined Patent Application PublicationNos. 2-71556, 2-188966, and 3-145761).

Using a metal in the gate electrode instead of polysilicon helpssuppress depletion and decrease the resistance of the gate electrode.However, this requires a production process that always takes intoaccount metal contamination caused by the metal gate in the stepssubsequent to formation of the metal gate.

To produce existing MOS transistors, a metal-gate-last process in whicha metal gate is formed after a high temperature process is put intopractice so as to avoid incompatibility between the metal gate processand the high temperature process (for example, refer to A 45 nm LogicTechnology with High-k+Metal Gate Transistors, Strained Silicon, 9 CuInterconnect Layers, 193 nm Dry Patterning, and 100% Pb-free Packaging,IEDM2007 K. Mistry et. al, pp 247-250).

That is, a MOS transistor has been made by forming a gate withpolysilicon, depositing an interlayer insulating film on thepolysilicon, exposing the polysilicon gate by chemical mechanicalpolishing (CMP), etching the polysilicon gate, and depositing a metal.In order to avoid incompatibility between the metal gate process and thehigh temperature process, it is also necessary for producing a SGT toemploy a metal-gate-last process with which a metal gate is formed aftera high temperature process. Since the upper part of a pillar-shapedsilicon layer of a SGT is located at a position higher than the gate,some adjustment must be made in employing the metal-gate-last process.

An existing MOS transistor uses a first insulating film in order todecrease the parasitic capacitance between the gate line and thesubstrate. For example, in making a FINFET (refer to High performance22/20 nm FinFET CMOS devices with advanced high-K/metal gate scheme,IEDM2010, CC. Wu, et. al, 27.1.1-27.1.4, for example), a firstinsulating film is formed around one fin-shaped semiconductor layer andthen etched back so as to expose the fin-shaped semiconductor layer andto decrease the parasitic capacitance between the gate line and thesubstrate. In making a SGT also, a first insulating film is needed toreduce the parasitic capacitance between the gate line and thesubstrate. Since a SGT includes not only a fin-shaped semiconductorlayer but also a pillar-shaped semiconductor layer, some adjustment mustbe made in order to form a pillar-shaped semiconductor layer.

According to a known SGT manufacturing process, a contact hole for apillar-shaped silicon layer is formed by etching through a mask and thencontact holes for a gate line and a planar silicon layer are formed byetching through a mask (for example, refer to Japanese Unexamined PatentApplication Publication No. 2011-258780). That is, conventionally, twomasks have been used for forming contacts.

SUMMARY OF THE INVENTION

The present invention has been made under the above-describedcircumstances. An object of the present invention is to provide asemiconductor device having reduced parasitic capacitance between a gateline and a substrate.

A method for producing a semiconductor device according to a firstaspect of the present invention includes:

a first step of forming a fin-shaped silicon layer on a siliconsubstrate, forming a first insulating film around the fin-shaped siliconlayer, and forming a pillar-shaped silicon layer in an upper portion ofthe fin-shaped silicon layer so that a width of the pillar-shapedsilicon layer is equal to a width of the fin-shaped silicon layer;

the second step of implanting an impurity to an upper portion of thepillar-shaped silicon layer, an upper portion of the fin-shaped siliconlayer, and a lower portion of the pillar-shaped silicon layer to formdiffusion layers, the second step being performed after the first step;

the third step of forming a gate insulating film, a polysilicon gateelectrode, a polysilicon gate line, and a polysilicon gate pad so thatthe gate insulating film covers the periphery and an upper portion ofthe pillar-shaped silicon layer and the polysilicon gate electrodecovers the gate insulating film, that, after the formation of thepolysilicon gate electrode, the polysilicon gate line, and thepolysilicon gate pad, an upper surface of the polysilicon is located ata position higher than the gate insulating film located on the diffusionlayer in the upper portion of the pillar-shaped silicon layer, and thatthe width of the polysilicon gate electrode and the width of thepolysilicon gate pad are larger than the width of the polysilicon gateline, the third step being performed after the second step;

the fourth step of forming a silicide in an upper portion of thediffusion layer in the upper portion of the fin-shaped silicon layer,the fourth step being performed after the third step;

the fifth step of depositing an interlayer insulating film, exposing thepolysilicon gate electrode, polysilicon gate line, and the polysilicongate pad, and etching the polysilicon gate electrode, polysilicon gateline, and the polysilicon gate pad, and depositing a metal layer so asto form a metal gate electrode, a metal gate line, and a metal gate pad,the metal gate line extending in a direction perpendicular to thefin-shaped silicon layer and being connected to the metal gateelectrode, the fifth step being performed after the fourth step; and

the sixth step of forming a contact directly connected to the diffusionlayer in the upper portion of the pillar-shaped silicon layer, the sixthstep being performed after the fifth step.

Preferably, a first resist for forming the fin-shaped silicon layer onthe silicon substrate is formed, the silicon substrate is etched byusing the first resist so as to form the fin-shape silicon layer, andthen the first resist is removed.

Preferably, the first insulating film is deposited around the fin-shapedsilicon layer and the first insulating film is etched back to expose theupper portion of the fin-shaped silicon layer.

Preferably, a second resist is formed so as to perpendicularly intersectthe fin-shaped silicon layer, the fin-shaped silicon layer is etched byusing the second resist, and the second resist is removed so that thepart where the fin-shaped silicon layer and the second resist intersectforms the pillar-shaped silicon layer.

Preferably, a second oxide film is deposited from above a structure thatincludes the fin-shaped silicon layer formed on the silicon substrate,the first insulating film formed around the fin-shaped silicon layer,and the pillar-shaped silicon layer formed in the upper portion of thefin-shaped silicon layer, a first nitride film is formed on the secondoxide film, and the first nitride film is etched so as to be left as asidewall.

Preferably, an impurity is then implanted so as to form the diffusionlayers in the upper portion of the pillar-shaped silicon layer and theupper portion of the fin-shaped silicon layer, the first nitride filmand the second oxide film are removed, and then a heat-treatment isperformed.

In a structure that includes the fin-shaped silicon layer formed on thesilicon substrate, the first insulating film formed around thefin-shaped silicon layer, the pillar-shaped silicon layer formed in theupper portion of the fin-shaped silicon layer, the diffusion layerformed in the upper portion of the fin-shaped silicon layer and thelower portion of the pillar-shaped silicon layer, and the diffusionlayer formed in the upper portion of the pillar-shaped silicon layer,

preferably, a gate insulating film is formed, polysilicon is depositedand planarized, and an upper surface of the planarized polysilicon islocated at a position higher than the gate insulating film on thediffusion layer in the upper portion of the pillar-shaped silicon layer;and

preferably, a second nitride film is deposited, a third resist forforming the polysilicon gate electrode, the polysilicon gate line, andthe polysilicon gate pad is formed, the second nitride film and thepolysilicon are etched by using the third resist so as to form thepolysilicon gate electrode, the polysilicon gate line, and thepolysilicon gate pad, the gate insulating film is etched, and then thethird resist is removed.

Preferably, a third nitride film is deposited and etched so as to beleft as a sidewall, a metal layer is deposited, and a silicide is formedin an upper portion of the diffusion layer in the upper portion of thefin-shaped silicon layer.

Preferably, a fourth nitride film is deposited, an interlayer insulatingfilm is deposited and planarized, the polysilicon gate electrode, thepolysilicon gate line, and the polysilicon gate pad are exposed, thepolysilicon gate electrode, the polysilicon gate line, and thepolysilicon gate pad are removed, and spaces where the polysilicon gateelectrode, the polysilicon gate line, and the polysilicon gate pad hadexisted are filled with a metal, and the metal is etched to expose thegate insulating film on the diffusion layer in the upper portion of thepillar-shaped silicon layer and to form the metal gate electrode, themetal gate line, and the metal gate pad.

Preferably, a fifth nitride film thicker than a half of the width of thepolysilicon gate line and thinner than a half of the width of thepolysilicon gate electrode and a half of the width of the polysilicongate pad is deposited to form contact holes on the pillar-shaped siliconlayer and the metal gate pad.

A semiconductor device according to a second aspect of the presentinvention includes a fin-shaped silicon layer on a silicon substrate;

a first insulating film around the fin-shaped silicon layer;

a pillar-shaped silicon layer on the fin-shaped silicon layer, a widthof the pillar-shaped silicon layer being equal to a width of thefin-shaped silicon layer;

a first diffusion layer in an upper portion of the fin-shaped siliconlayer and in a lower portion of the pillar-shaped silicon layer;

a second diffusion layer in an upper portion of the pillar-shapedsilicon layer;

a gate insulating film around the pillar-shaped silicon layer;

a metal gate electrode around the gate insulating film;

a metal gate line extending in a direction perpendicular to thefin-shaped silicon layer and connected to the metal gate electrode;

a metal gate pad connected to the metal gate line;

a contact on the metal gate line; and

a nitride film on an entire top surface of the metal gate electrode andthe metal gate line except the bottom of the contact

and a nitride film on the sidewall of the metal gate electrode and gateline;

wherein a verticle thickness of the nitride film on the entire topsurface of the metal gate electrode and the metal gate line relative tothe substrate is greater than a horizontal thickness of the nitride filmon the sidewall of the metal gate electrode and gate line relative tothe substrate, and

wherein a height of the top surface of the metal gate electrode is equalto a height of the top surface of the metal gate line relative to thesubstrate.

According to the present invention, a method for producing asemiconductor device, the method being a gate-last process capable ofreducing the parasitic capacitance between the gate line and thesubstrate and a semiconductor device produced through this method can beprovided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 2 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 3 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 4 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 5 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 6 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 7 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 8 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 9 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 10 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 11 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 12 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 13 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 14 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 15 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 16 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 17 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 18 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 19 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 20 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 21 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 22 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 23 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 24 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 25 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 26 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 27 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 28 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 29 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 30 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 31 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 32 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 33 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 34 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 35 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 36 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 37 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a);

FIG. 38 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a); and

FIG. 39 includes part (a) which is a plan view of a semiconductor deviceaccording to the present invention, part (b) which is a cross-sectionalview taken along line X-X′ in (a), and part (c) which is across-sectional view taken along line Y-Y′ in (a).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A method for producing a semiconductor device according to an embodimentof the present invention and a semiconductor device obtained by themethod will now be described with reference to drawings.

A production method that includes forming a fin-shaped silicon layer ona silicon substrate, forming a first insulating film around thefin-shaped silicon layer, and forming a pillar-shaped silicon layer inan upper portion of the fin-shaped silicon layer is described below.

First, as shown in FIG. 2, a first resist 102 for forming a fin-shapedsilicon layer is formed on a silicon substrate 101.

Next, as shown in FIG. 3, the silicon substrate 101 is etched to form afin-shaped silicon layer 103. Although a fin-shaped silicon layer isformed by using a resist as a mask here, a hard mask such as an oxidefilm or a nitride film may be used instead of the resist.

Next, as shown in FIG. 4, the first resist 102 is removed.

Then, as shown in FIG. 5, a first insulating film 104 composed of anoxide is formed around the fin-shaped silicon layer 103 by deposition.The first insulating film may be an oxide film formed by a high-densityplasma process or an oxide film formed by a low-pressure chemical vapordeposition process instead of one made by such a deposition method.

As shown in FIG. 6, the first insulating film 104 is etched back toexpose an upper portion of the fin-shaped silicon layer 103. The processup to here is the same as the process of making a fin-shaped siliconlayer in PTL 2.

As shown in FIG. 7, a second resist 105 is formed to perpendicularlyintersect the fin-shaped silicon layer 103. The part where thefin-shaped silicon layer 103 and the second resist 105 intersect forms apillar-shaped silicon layer. Since a line-shaped resist can be used assuch, the possibility of the break of the resist after formation of apattern is low and the process becomes stable.

Then, as shown in FIG. 8, the fin-shaped silicon layer 103 is shaped byetching. As a result, the part where the fin-shaped silicon layer 103and the second resist 105 intersect forms a pillar-shaped silicon layer106. Accordingly, the width of the pillar-shaped silicon layer 106 isequal to the width of the fin-shaped silicon layer 103. As a result, astructure in which the pillar-shaped silicon layer 106 is formed in theupper portion of the fin-shaped silicon layer 103 and the firstinsulating film 104 is formed around the fin-shaped silicon layer 103 isformed.

As shown in FIG. 9, the second resist 105 is removed.

A method for forming diffusion layers by implanting an impurity into anupper portion of the pillar-shaped silicon layer, an upper portion ofthe fin-shaped silicon layer, and a lower portion of the pillar-shapedsilicon layer is described below.

That is, as shown in FIG. 10, a second oxide film 107 is formed bydeposition and a first nitride film 108 is formed. In order to preventthe impurity from being implanted into the sidewall of the pillar-shapedsilicon layer, the first nitride film 108 need be formed only on thesidewall of the pillar-shaped silicon layer so as to have a sidewallshape. Since the upper part of the pillar-shaped silicon layer will becovered with a gate insulating film and a polysilicon gate electrode inthe subsequent steps, it is desirable to form a diffusion layer in theupper portion of the pillar-shaped silicon layer before thepillar-shaped silicon layer is covered as such.

Then, as shown in FIG. 11, the first nitride film 108 is etched so as tobe left as a sidewall.

Next, as shown in FIG. 12, an impurity such as arsenic, phosphorus, orboron is implanted to form a diffusion layer 110 in the upper portion ofthe pillar-shaped silicon layer and diffusion layers 109 and 111 in theupper portion of the fin-shaped silicon layer 103.

Then, as shown in FIG. 13, the first nitride film 108 and the secondoxide film 107 are removed.

Referring now to FIG. 14, a heat-treatment is performed. The diffusionlayers 109 and 111 in the upper portion of the fin-shaped silicon layer103 come into contact with each other so as to form a diffusion layer112. As a result of the above-described steps, an impurity is implantedinto the upper portion of the pillar-shaped silicon layer 106, the upperportion of the fin-shaped silicon layer 103, and the lower portion ofthe pillar-shaped silicon layer 106 so as to form the diffusion layers110 and 112.

A method for preparing a polysilicon gate electrode, a polysilicon gateline, and a polysilicon gate pad by using polysilicon will now bedescribed. According to this method, an interlayer insulating film isfirst deposited and then a polysilicon gate electrode, a polysilicongate line, and a polysilicon gate pad are exposed by chemical mechanicalpolishing (CMP). Thus, it is essential that the upper portion of thepillar-shaped silicon layer remain unexposed despite CMP.

In other words, as shown in FIG. 15, a gate insulating film 113 isformed, a polysilicon 114 is deposited, and the surface thereof isplanarized. The upper surface of the polysilicon 114 after planarizationis to come at a position higher than the gate insulating film 113 on thediffusion layer 110 in the upper portion of the pillar-shaped siliconlayer 106. In this manner, the upper portion of the pillar-shapedsilicon layer can remain unexposed despite CMP, during which apolysilicon gate electrode 114 a, a polysilicon gate line 114 b, and apolysilicon gate pad 114 c become exposed and which is performed afterdeposition of the interlayer insulating film.

Next, a second nitride film 115 is deposited. The second nitride film115 prevents formation of a silicide in the upper portions of thepolysilicon gate electrode 114 a, polysilicon gate line 114 b, andpolysilicon gate pad 114 c during the process of forming a silicide inthe upper portion of the fin-shaped silicon layer 103.

Next, as shown in FIG. 16, a third resist 116 for forming thepolysilicon gate electrode 114 a, the polysilicon gate line 114 b, andthe polysilicon gate pad 114 c is formed. The polysilicon gate pad 114 cis preferably arranged so that the part that forms a gate lineperpendicularly intersects the fin-shaped silicon layer 103 in order todecrease the parasitic capacitance between the gate line and thesubstrate. The width of the polysilicon gate electrode 114 a and thewidth of the polysilicon gate pad 114 c are preferably larger than thewidth of the polysilicon gate line 114 b.

Then, as shown in FIG. 17, the second nitride film 115 is formed byetching.

Then, as shown in FIG. 18, the polysilicon 114 is etched to form thepolysilicon gate electrode 114 a, the polysilicon gate line 114 b, andthe polysilicon gate pad 114 c.

Then, as shown in FIG. 19, the gate insulating film 113 is etched so asto remove the bottom portion of the gate insulating film 113.

Then, as shown in FIG. 20, the third resist 116 is removed.

The polysilicon gate electrode 114 a, the polysilicon gate line 114 b,and the polysilicon gate pad 114 c are thus formed through the stepsdescribed above.

The upper surface of the polysilicon after forming the polysilicon gateelectrode 114 a, the polysilicon gate line 114 b, and the polysilicongate pad 114 c is located at a position higher than the gate insulatingfilm 113 on the diffusion layer 110 in the upper portion of thepillar-shaped silicon layer 106.

A method for forming a silicide in the upper portion of the fin-shapedsilicon layer will now be described. This method is characterized inthat no silicide is formed in the upper portions of the polysilicon gateelectrode 114 a, the polysilicon gate line 114 b, and the polysilicongate pad 114 c, and the diffusion layer 110 in the upper portion of thepillar-shaped silicon layer 106. It is not preferable to form a silicidein the diffusion layer 110 in the upper portion of the pillar-shapedsilicon layer 106 since the number of steps in the method will increase.

First, as shown in FIG. 21, a third nitride film 117 is deposited.

Next, as shown in FIG. 22, the third nitride film 117 is etched to beleft as a sidewall.

Then, as shown in FIG. 23, a metal such as nickel or cobalt is depositedto form a silicide 118 in the upper portion of the diffusion layer 112in the upper portion of the fin-shaped silicon layer 103. Since thepolysilicon gate electrode 114 a, the polysilicon gate line 114 b, andthe polysilicon gate pad 114 c are covered with the third nitride film117 and the second nitride film 115 and the diffusion layer 110 in theupper portion of the pillar-shaped silicon layer 106 is covered with thegate insulating film 113, the polysilicon gate electrode 114 a, and thepolysilicon gate line 114 b, no silicide is formed in these parts.

Through the steps described above, a silicide is formed in the upperportion of the fin-shaped silicon layer 103.

Next, a gate-last production process in which, after an interlayerinsulating film is deposited on the structure obtained through the stepsdescribed above, the polysilicon gate electrode 114 a, the polysilicongate line 114 b, and the polysilicon gate pad 114 c are exposed by CMPand removed by etching and then a metal is deposited is described.

First, as shown in FIG. 24, a fourth nitride film 119 is deposited toprotect the silicide 118.

Next, as shown in FIG. 25, an interlayer insulating film 120 isdeposited and the surface thereof is planarized by CMP.

Then, as shown in FIG. 26, the polysilicon gate electrode 114 a, thepolysilicon gate line 114 b, and the polysilicon gate pad 114 c areexposed by CMP.

Then, as shown in FIG. 27, the polysilicon gate electrode 114 a, thepolysilicon gate line 114 b, and the polysilicon gate pad 114 c areetched. They are preferably wet-etched.

Then, as shown in FIG. 28, a metal 121 is deposited and the surfacethereof is planarized so as to fill the spaces where the polysilicongate electrode 114 a, the polysilicon gate line 114 b, and thepolysilicon gate pad 114 c had existed with the metal 121. Atomic layerdeposition is preferably employed to fill the spaces.

Then, as shown in FIG. 29, the metal 121 is etched to expose the gateinsulating film 113 on the diffusion layer 110 in the upper portion ofthe pillar-shaped silicon layer 106. As a result, a metal gate electrode121 a, a metal gate line 121 b, and a metal gate pad 121 c are formed.

The steps described above constitute the method for producing asemiconductor device by a gate-last technique of depositing metal layersafter etching the polysilicon gate exposed by CMP after deposition ofthe interlayer insulating film.

A method for forming contacts will now be described. Here, since nosilicide is formed in the diffusion layer 110 in the upper portion ofthe pillar-shaped silicon layer 106, the contact is directly connectedto the diffusion layer 110 in the upper portion of the pillar-shapedsilicon layer 106.

That is, first, as shown in FIG. 30, a fifth nitride film 122 isdeposited so that the fifth nitride film 122 is thicker than a half ofthe width of the polysilicon gate line 114 b and thinner than a half ofthe width of the polysilicon gate electrode 114 a and a half of thewidth of the polysilicon gate pad 114 c. As a result, contact holes 123and 124 are formed on the pillar-shaped silicon layer 106 and the metalgate pad 121 c. The fifth nitride film 122 and the gate insulating film113 at the bottom portions of the contact holes 123 and 124 will beremoved by a subsequent step of etching the nitride film. Accordingly, amask for forming the contact hole 123 on the pillar-shaped silicon layerand the contact hole 124 on the metal gate pad 121 c is not needed.

Next, as shown in FIG. 31, a fourth resist 125 for forming a contacthole 126 on the fin-shaped silicon layer 103 is formed.

Then, as shown in FIG. 32, the fifth nitride film 122 and the interlayerinsulating film 120 are etched to form the contact hole 126.

Then, as shown in FIG. 33, the fourth resist 125 is removed.

Then, as shown in FIG. 34, the fifth nitride film 122, the fourthnitride film 119, and the gate insulating film 113 are etched to exposethe silicide 118 and the diffusion layer 110.

Then, as shown in FIG. 35, a metal is deposited to form contacts 127,128, and 129.

Through the steps described above, the contacts 127, 128, and 129 can beformed in the semiconductor device. According to this production method,no silicide is formed in the diffusion layer 110 in the upper portion ofthe pillar-shaped silicon layer 106 and thus the contact 128 is directlyconnected to the diffusion layer 110 in the upper portion of thepillar-shaped silicon layer 106.

The method for forming metal wiring layers will now be described.

First, as shown in FIG. 36, a metal 130 is deposited.

Next, as shown in FIG. 37, fifth resists 131, 132, and 133 for formingmetal wirings are formed.

Then, as shown in FIG. 38, the metal 130 is etched to form metal wirings134, 135, and 136.

Then, as shown in FIG. 39, the fifth resists 131, 132, and 133 areremoved.

Through the steps described above, the metal wirings 134, 135, and 136which constitute metal wiring layers are formed.

A semiconductor device produced by the production method described aboveis shown in FIG. 1.

The semiconductor device shown in FIG. 1 includes the fin-shaped siliconlayer 103 formed on the silicon substrate 101, the first insulating film104 formed around the fin-shaped silicon layer 103, the pillar-shapedsilicon layer 106 formed on the fin-shaped silicon layer 103, the widthof the pillar-shaped silicon layer 106 being equal to the width of thefin-shaped silicon layer 103, and the diffusion layer 112 formed in theupper portion of the fin-shaped silicon layer 103 and in the lowerportion of the pillar-shaped silicon layer 106.

The semiconductor device shown in FIG. 1 further includes the diffusionlayer 110 formed in the upper portion of the pillar-shaped silicon layer106, the silicide 118 formed in the upper portion of the diffusion layer112 in the upper portion of the fin-shaped silicon layer 103, the gateinsulating film 113 formed around the pillar-shaped silicon layer 106,the metal gate electrode 121 a formed around the gate insulating film,the metal gate line 121 b extending in a direction perpendicular to thefin-shaped silicon layer 103 and being connected to the metal gateelectrode 121 a, and the metal gate pad 121 c connected to the metalgate line 121 b. The width of the metal gate electrode 121 a and thewidth of the metal gate pad 121 c are larger than the width of the metalgate line 121 b.

The semiconductor device shown in FIG. 1 has a structure in which thecontact 128 is formed on the diffusion layer 110 and the diffusion layer110 is directly connected to the contact 128.

In sum, according to this embodiment of the present invention, a methodfor producing a SGT, which is a gate-last process capable of decreasingthe parasitic capacitance between the gate line and the substrate andwhich uses only one mask for forming contacts is provided. A SGTstructure obtained by this method is also provided.

Since the method for producing a semiconductor device of the embodimentis based on a known method for producing FINFET, the fin-shaped siliconlayer 103, the first insulating film 104, and the pillar-shaped siliconlayer 106 can be easily formed.

According to a known method, a silicide is formed in the upper portionof a pillar-shaped silicon layer. Since the polysilicon depositiontemperature is higher than the temperature for forming the silicide, thesilicide needs to be formed after forming the polysilicon gate. Thus, inthe case where a silicide is to be formed in the upper portion of asilicon pillar, the steps of forming a polysilicon gate, forming a holein the upper portion of the polysilicon gate electrode, forming asidewall with an insulating film on the sidewall of that hole, forming asilicide, and filling the hole with an insulating film are needed. Thus,there is a problem in that the number of steps in the method willincrease.

In contrast, according to the embodiment described above, diffusionlayers are formed before forming the polysilicon gate electrode 114 aand the polysilicon gate line 114 b and the pillar-shaped silicon layer106 is covered with the polysilicon gate electrode 114 a so that thesilicide is formed in the upper portion of the fin-shaped silicon layer103 only. Then a gate is formed with a polysilicon, the interlayerinsulating film 120 is deposited, the polysilicon gate is exposed bychemical mechanical polishing (CMP), and then the polysilicon gate isetched, followed by deposition of a metal. Such a metal-gate-lastproduction method can be used in this embodiment. Thus, according tothis method for producing a semiconductor device, a SGT having a metalgate can be easily produced.

The width of the polysilicon gate electrode 114 a and the width of thepolysilicon gate pad 114 c are larger than the width of the polysilicongate line 114 b. Furthermore, the fifth nitride film 122 thicker than ahalf of the width of the polysilicon gate line 114 b and thinner than ahalf of the width of the polysilicon gate electrode 114 a and a half ofthe width of the polysilicon gate pad 114 c are deposited in a holeformed by etching the polysilicon gate after forming the metal gate.Thus, the contact holes 123 and 124 can be formed on the pillar-shapedsilicon layer 106 and the metal gate pad 121 c, and thus aconventionally required etching step that forms a contact hole in thepillar-shaped silicon layer through a mask is no longer needed. In otherwords, only one mask is needed to form contacts.

It should be understood that various other embodiments and modificationsare possible without departing from the spirit and scope of the presentinvention in a broad sense. The embodiment described above is merelyillustrative and does not limit the scope of the present invention.

1. A semiconductor device comprising: a fin-shaped silicon layer on asilicon substrate; a first insulating film around the fin-shaped siliconlayer; a pillar-shaped silicon layer on the fin-shaped silicon layer; afirst diffusion layer in an upper portion of the fin-shaped siliconlayer and in a lower portion of the pillar-shaped silicon layer; asecond diffusion layer in an upper portion of the pillar-shaped siliconlayer; a gate insulating film around the pillar-shaped silicon layer; ametal gate electrode around the gate insulating film; a metal gate lineextending in a direction perpendicular to the fin-shaped silicon layerand connected to the metal gate electrode; a metal gate pad connected tothe metal gate line; a contact on the metal gate line; and a nitridefilm on an entire top surface of the metal gate electrode and the metalgate line except the bottom of the contact and a nitride film on thesidewall of the metal gate electrode and gate line; wherein a verticalthickness of the nitride film on the entire top surface of the metalgate electrode and the metal gate line relative to the substrate isgreater than a horizontal thickness of the nitride film on the sidewallof the metal gate electrode and gate line relative to the substrate, andwherein a height of the top surface of the metal gate electrode is equalto a height of the top surface of the metal gate line relative to thesubstrate.